Method of data compression including compression of video data

ABSTRACT

A data processing system includes a subband decomposition of a source signal by encoding of the significant pyramid-type subband representation. While encoding process, M-array is used for initialization of set of arrays S i  (arrays of solution bits), which define the order of creating output data streams. Output data streams contain an encoded significance map and values of (significant) non-zero subband decomposition coefficients adapted for successive quantization and entropy encoding.

INCORPORATION BY REFERENCE

U.S. Pat. Nos. 5,321,776 to Shapiro and 5,764,807 to Pearlman et al. are both hereby incorporated by reference in their entirety.

Reference is also made to U.S. patent application No. ______, filed Jun. 29, 2005, entitled, “METHOD OF VIDEO DATA TRANSMITTING”, by Andrey V. Zurov et al.

The present application claims the benefit of Provisional Patent Application No. 60/584,102, filed Jun. 30, 2004.

The disclosure of both above-identified applications are incorporated herein in their entirety, by reference.

DESCRIPTION

1. Field of the Invention

The invention lies in the field of data compression technique, in particular, it can be used for image and video data compression.

2. Background of the Invention

At present different means and methods are used for data compression. When solving the problems of image data transmission in photo or video formats and video data, the choice of this or that compression method is determined by the set of requirements for the quality of the image being transmitted and by data transfer rate limitations. If an image is transferred using the channel with low capacity, the main factor for the choice of optimal data compression method is its capability to determine significant data out of the general data flow and re-organize the information being transmitted so that the significant image data get the priority when being sent using transmission channel. In general, any data compression methods should decrease greatly the abundance of the information being transmitted in order to transmit the data with the highest authenticity degree using the minimal possible number of bit necessary for forming, transmitting and following recording of the data flow.

Nowadays the widest prospects of practical use have image data compression methods based on the pyramidal presentation of initial image decomposition coefficients in spatial-scale subbands. Such pyramidal representation can be achieved by means of multi resolution analysis. The result of the mentioned analysis is creating of hierarchical tree that has one root and final number of connected to it nodes, called descendants. As the ground for decomposition, the wavelet functions family is used (see “An Embedded Wavelet Hierarchical Image Coder” Jerome M. Shapiro, International Conference of Acoustic, Speech and Signal Processing, Mar. 1992). The image spectrum, received as the result of wavelet transformation application, due to the peculiarities of the ground applied, enables to get information not only about the array of initial data in general, but about its separate parts as well. This feature applied to the image allows using methods of controlled data compression for separate parts of the image.

The peculiarity of spectrum coefficients of image data decomposition is statistically true tendency to their decrease with the increase in spatial frequency. At this the simplest but evidently not optimal compression method is filtering of array of image spectrum coefficients by means of their comparison to one another with the set threshold value and the following declaration of the coefficients, the values of which are less than the threshold value, “insignificant” for the following encoding. There are methods with deeper analysis of spectrum coefficients “significance”. In particular, there is a method of data compression (the U.S. Pat. No. 5,321,776, issued at Jun. 14, 1994) based on the consistent examination of the tree nodes and detection of so called “positive symbol” in case the decomposition coefficient in this node is significant, i.e. the coefficient exceeds the threshold level and positive; “negative symbol”, that indicates that the spectrum coefficient in the node is significant and negative; isolated zero symbol for the node which spectrum coefficient is insignificant, i.e. does not exceed the threshold level, but which has at least one descendant, the spectrum coefficient of which, in its turn, exceeds the threshold level; and zero tree symbol for the node which spectrum coefficient is insignificant and which has no single descendant the spectrum coefficients of which are significant for the threshold level.

In order to increase the compression degree and data processing rate, the method of hierarchal tree division into multitudes of group sorting out of hierarchal tree was introduced (see the U.S. Pat. No. 5,764,807, issued at Jun. 9, 1998). In this patent the method of data encoding is described, according to which when consistently examining the tree from root to descendants, the decomposition spectrum coefficients in each node are compared to the current value of the threshold; after that they are added to one of the three groups: group of significant, i.e. exceeding the threshold coefficients; group of insignificant coefficients, i.e. coefficients the values of which are less than the threshold value; and group of insignificant descendants multitude. The mentioned group of insignificant coefficients multitude is characterized by its own root node and internal hierarchal tree that is created within the spectral subband. This method includes the check up operation for significance of root node descendants in each multitude of insignificant coefficients in cases when the spectrum coefficient of significant descendant of the root node descendants is at least equal to the set threshold value. At that for each root node of insignificant coefficients multitude, which has at least one significant descendant, the descendants of root node descendant is checked for significance in cases when the spectrum coefficient of significant descendant of the root node descendants is at least equal to the set threshold value.

The central concept of the said methods is the notion of “zero tree”. The tree is considered to be zero for the threshold if spectrum coefficients related to all tree nodes including the root are insignificant. Both methods consider the set of thresholds and encode the whole tree-like structure for each set. At that, data compression is achieved due to the fact that for encoding of zero tree it is necessary to encode the coordinates of its apex only; that is why the more zero trees the hierarchal structure of spectrum coefficients of data decomposition contains, the more compact and effective this structure is encoded.

Encoding of data flow with the help of well-known methods has a drawback that is most vividly revealed when transmitting information using low capacity channels, for example, wireless communication channels. The essence of this drawback is low quality of image restored after transmission. The reason for the drawback is that when realizing the methods described above, the flow being transmitted is formed out of initial distribution of spectrum decomposition coefficients without any preliminary reorganization. Besides, spectrum coefficients in different scales and in different frequency subbands in the mentioned methods are equivalent. The last reason means that when forming the data flow the largest coefficients are transmitted in the first place regardless of subband they belong to. At such approach, if a great number of large coefficients is concentrated in high frequency subbands (it happens if an image contains many small contrast details), they will get into the outer flow in the first place. Consequently, at the beginning of the flow data of small contrast details, which are, as a rule, of little importance, will be transmitted; data of main low frequency and more important changes will get into the flow later and may be lost or transmitted with lower accuracy.

The objective of the invention is quality improvement of image being transmitted.

SUMMARY OF THE INVENTION

The claimed method is an encoding procedure of hierarchal system of initial image spectrum decomposition coefficients with the help of wavelet subband filter. As the result of the wavelet transformation applied consequently to lines and columns of an image the spectrum coefficients subbands D are formed. Successive application of such transformation to low frequency subband at each decomposition level forms a hierarchal structure of coefficients. To each coefficient in the hierarchal structure correspond the coefficients with higher degree of precision. At that coefficient, which corresponds to the previous decomposition level is called an “ancestor”; coefficients, which correspond to the next decomposition level and related to the “ancestor” are called its “descendants”. Coefficients of spectrum decomposition are real numbers and are characterized by modulus and sign. When encoding data within the claimed method, bit array of the signs of initial image decomposition spectrum coefficients Z is formed; the components of the array have 0 values if corresponding spectrum coefficient of decomposition D is nonnegative. Components of the array of the same signs are equal to 1 in cases the corresponding spectrum coefficients of decomposition are negative.

Then the decomposition coefficients are evaluated by significance criterion and for this purpose an indexed set of threshold arrays T_(i), where I is an array index. Array T_(i) is a basic threshold array. When array index increases by 1, the values of arrays components in the set decrease twice T_(i)=T₀/2^(i). The essential attribute of the claimed method is the procedure of reorganization of spectrum coefficients array. For its realization so called “rival array” of coefficients M is formed. The formation of the array is carried out by successive transition from tree nodes corresponding to the last decomposition level, and which do not have the descendants, to their ancestor. At that transition the ancestor is given the value of the maximum coefficient from the coefficients-descendants of the node at all spectrum subbands of decomposition, rationed by the value of the corresponding threshold T₀.

Then the claimed method contains the procedure of indexed bit arrays S_(i) set formation, components of which regulate the order of priority of sending data to the flow. Components of the arrays are declared zero, when the value of spectrum coefficient of rival array M in the tree node is less than threshold value T_(i). In case the value of spectrum coefficient of rival array exceeds or is equal to threshold value, component of the array is declared to be equal to 1. Then the array of spectrum coefficients D of initial image decomposition is transformed into bit code represented by arrays set B_(i), after that the resulting data flow is formed as a set of coefficients of the mentioned above arrays.

For the purpose of additional data compression on the account of correlations between the mentioned coefficients the indexed set of vector arrays V_(i) is formed, components of which for any chosen tree node are the components of components of S_(i) and B_(i) arrays on the descendants of the given node and components of Z array on that descendants of the given node, for which B_(i)=1. Then the data flows of the mentioned arrays are formed and subject to entropy coding for the purpose of elimination of excessiveness. B_(i)

Besides, in the claimed invention in order to improve the quality of the image being transmitted it is proposed to form basic threshold array by means of increase the values of its coefficients twice at each transition to spectrum subband of higher level.

The claimed succession of operations of the method secures the quality improvement of image data transfer at the expense of data reorganization and increased number of zero trees, and also at the expense of ascribing image spectrum low frequency constituents to the beginning of the flow.

SHORT DESCRIPTION OF THE DRAWING

On FIG. 1 the scheme of multilevel spectrum coefficients into subbands according to the principles of the invention is shown.

On FIG. 2 the succession of initial image decomposition operations into spectrum subbands is shown.

On FIG. 3-6 block scheme of different aspects of operations according to the claimed invention is illustrated.

On FIG. 7 the structure of components of basis threshold array T₀ is shown.

FIGS. 8-21 illustrate alternative and/or detailed concepts of the present application.

DETAILED DESCRIPTION OF THE INVENTION

Let us suppose that we have an image of 2^(N)×2^(N) pixels. Initial image possesses utmost high spatial capacity and depicts the smallest details. Applying spectral decomposition of lines and columns of the image using wavelet-functions basis and dividing each spectrum into low frequency and high frequency constituents we get four arrays of spectrum coefficients with size 2^(N-1)×2^(N-1). These arrays contain: low frequency coefficients of lines and columns decomposition, included in the LL1 array; low frequency coefficients of lines decomposition and high frequency coefficients of columns decomposition, included in the LH1 array; high frequency coefficients of lines decomposition and low frequency coefficients of columns decomposition, included in the HL1 array; and high frequency coefficients of lines and columns decomposition, included in the HH1 array. LL1 array can be subject to further decomposition into low-high frequency spectrum subband; as the result, four arrays LL2, LH2, HL2 and HH2 will be formed, the size of which will be twice less than the previous one, i.e. 2^(N-2)×2^(N-2). The process of spectrum subband formation reflects the successive transition to examination of lower and lower frequency spectrum constituents of initial image spectrum. This process is terminated at N-step when the size of LLN array becomes equal to 1×1. The scheme of the spectrum transformation described above is illustrated on FIG. 1, and succession of subbands formation is illustrated on FIG. 2.

On FIG. 2 the succession of transformation of initial data two-dimension array 1 is presented, by means of filtering of low spatial frequencies in lines by means of filter 2 and of high spatial frequencies in lines with the help of filter 8. Then the signal from output of filter 2 is transformed by filtering of low spatial frequencies in columns using filter 4 and of high spatial frequencies I columns using filter 6, and the signal from output of filter 8 is transformed by filtering of low spatial frequencies in columns using filter 10 and of high spatial frequencies using filter 12. At outputs of filters 4, 6, 10 and 12 data arrays LL, HL, LH and HH are formed, it should be noted, that the size of each array is twice less than the size of initial data array. Further, the procedure described above is applied to LL array until the size of low frequency subband will be the minimal possible. The object, received as the result of successive spectrum decomposition, looks like hierarchal tree, components in the nodes of which are connected to one another with ancestor-descendant relations. At that decomposition coefficient related to ancestor always corresponds to lower frequency constituent of the spectrum than the coefficient, related to descendant.

In the character of the functions, which are used for spectral decomposition of initial image, in this invention we propose to use wavelet subband filter. The choice of wavelet-functions basis, optimal from the point of view of quality of image being transmitted with set compression coefficient is a hard task. A number of criteria are known, which are followed when choosing the basis. To such functions smoothness of functions, accuracy of approximation, frequency selectivity of filter, energy distribution are referred.

When encoding the coefficient values of D spectrum decomposition of initial image, it is necessary to take into consideration absolute coefficient value and its sign. In order to transfer information about spectrum coefficients sign into the data flow, within the claimed method a separate bit array Z is formed, components of which are equal to 0 in those nodes, where D coefficients are nonnegative, and are equal to 1, correspondingly, in those nodes, where D coefficients are less than 0.

In order to carry out an effective data compression and to preserve high quality of the image being transmitted, it is necessary to reorganize D coefficients array and to transfer them to bit representation. For these purposes the sets of indexed threshold arrays T_(i) are formed, one of which is a basis threshold array T₀. For each separate tree node the components values of T_(i) and T₀ arrays are connected by the relation T_(i)=T₀/2^(i). The components values of T₀ array for nodes of LLN spectrum subband are determined in the encoding algorithm. For nodes of spectrum subbands corresponding to the previous decomposition levels, the components values of T₀ array are multiplied by two. In that way we secure the conditions for discrimination of high frequency constituents of image spectrum when reorganizing a spectrum coefficients array according to significance criterion.

In order to realize the mentioned procedure of reorganization according to the claimed invention the so-called “rival array” of coefficients M is formed. The formation of the array is carried out by means of successive transition from tree nodes, corresponding to the last level of decomposition, and which do not have descendants, to their ancestors. At that transition ancestor is given such M value that ratio M/T₀ in the tree node equals to maximum number received in division of descendants' coefficients of the node D for all spectrum decomposition subbands in values of the corresponding thresholds T₀. Formation of rival array plays a key role in the claimed method of data compression for quality improvement of the image being transferred.

In order to establish if the threshold T_(i) among descendants of the given node has a significant one, indexed set of bit arrays S_(i) is formed. Components of the arrays are declared to be zero if the value of spectrum coefficient of rival array M in the given tree node is less than threshold value T_(i). If the value of spectrum coefficient of rival array in the tree node equals or exceeds the threshold value, the component of the given array is declared to be equal to 1.

Further, the spectrum coefficients of initial image decomposition D are transformed into a bit code, represented by the set of arrays B_(i). Components values of these arrays for D number, corresponding to the given node, is calculated using the formula B_(i)=[2{|D|/T_(i-1)}], where figure brackets means operation of taking fractional part of a number, and square brackets—operation of taking whole part of a number.

For carrying out data encoding according to the principles of the invention it is necessary to determine the order of tree examination. It is proposed to examine tree nodes beginning from the lower decomposition level to higher, and within each tree level it is proposed to examine nodes according to the set for this level order of examination. The structure of the tree and the order of examination of its nodes are considered fixed during the encoding and decoding processes.

On FIG. 3 the succession of operations when transiting to the next level during tree examination is shown. In the first place 31 the current node and threshold index value i are set. Then 32 it is determined if there is a next node at the chosen threshold level that follows the current node according to the direction of the tree examination. In case there is, at the next step 33 the next level is considered current. After that 34 the check-up of bit arrays S values, which correspond to the current node and to its ancestor at the current and previous threshold levels is carried out. Namely, the next after the current node is considered the first after the current node according the direction of tree examination, for which either value S_(i-1)=0 and value S_(i-1)=1 for its ancestor, or value S_(i)=1 and value S_(i-1)=0 for its ancestor. If condition 34 is fulfilled, transition to the next node is considered fulfilled. If condition 34 is not fulfilled, then again 32 is determined if there is a next node at the chosen threshold level that follows the current node according to the direction of the tree examination.

On FIGS. 4-6 the process of data array encoding according to the principles of the invention is described. Before the beginning of encoding the L number of threshold arrays in the set is chosen, which equals to the number of bits in the maximal coefficient of spectrum decomposition D. At the first step 41 the value of threshold index is considered I=0, the current node is considered tree root, the threshold value T₀ is chosen so that S₀=1 and S⁻¹=0. Then 42 the value of vector array V₀, which was calculated in the tree root, is transferred to the flow. After that search and transition to the next tree node 43 according to the principles described above and shown on FIG. 3 is carried out. After check up for the next node existence 44, in case it exists, the next node is declared current 45 and the encoding process starts from input of operation 42. In case the next node is not detected, which is possible, for example, at the tree edges, the transition to the next threshold level 46 is carried out and tree root 51 is declared current node. On steps 52 and 54 the search and transition to the next tree node is carried out, after the next node was detected. Then the next node is declared current 54. Then the check ups of S_(i-1) values for the ancestor of the current node 55 and of the current node 55 a itself are successively realized. In case, the S_(i-1) value for the ancestor of the current node equals to 1, and S_(i-1) value for the current node equals to 0, the value of S_(i) array is transferred to the data flow for the given node 56. Then the check up of this value is realized 57. In case the value S_(i) for the current node equals to 1, the value of V_(i) array is additionally transferred to the data flow for the given node 58. After that the search and transition to the next tree node 52, 53 are realized according to the principles, described above and shown on FIG. 3.

In cases, as the result of carrying out operation 53 the next tree node is not determined, the tree root 61 is declared the current node. Then tree nodes are successively examined according to the set order of examination and it is established, if there is a next node after the current one according the direction of examination 62. In case such node exists, on the next step 63 the next node is determined as current. After that 64 the check up of the S_(i-1) bit array value, which corresponds to the ancestor of the current node. In case the S_(i-1) value for the ancestor of the current node equals to 1, the value of B_(i) array is transferred to the data flow for the current node 65. Then the check up of 1≦|D|/T_(i)<2 condition for the given node. If the given condition is fulfilled, then the value of the Z array for the given node is transferred to the data flow. In the opposite case the encoding process is sent back to the input of operation 62.

In cases the next after the current node according to the direction of tree examination is absent or if S_(i-1) for the ancestor of the current node equals to 0, the transition to the next threshold level 68 is carried out. Then based on the condition that index of the next in turn threshold level i does not exceed the value L, the encoding process is sent back to the input of operation 51.

On FIG. 7 the structure of the threshold array T₀ basis components is shown. In order for improvement of image quality being transmitted it is proposed to form basis threshold array by means of doubling coefficients values at each transition to spectrum subband of the higher level.

With continuing attention to the present application, disclosed below is the Comet Codec Operation Plan as shown in FIG. 8, where Comet Codec consists of three blocks:

-   -   Video Codec     -   Audio Codec     -   Network Kernel

All the three blocks interact in order to secure synchronized audio and video encoding and also for automatic adjustment of codecs when changing the communication channel or when the connection is terminated.

Video Codec

Video Codec carries out encoding and decoding using wavelets of video flows. The given processor has the following work cycle:

-   -   Preprocessing     -   Encoding of key frames     -   Compensating models     -   Decoding of key and compensated frames     -   Postprocessing

Preprocessing—the necessary video image preparation for the following encoding, i.e. enhancement of quality (on the basis of available from the previous frames statistics).

Encoding of key frames is carried out on the basis of developed video compression methods using wavelet technology.

Compensating methods enable to transmit greater number of frames due to the fact that only the difference between them is being transmitted. This method should be closely connected with Preprocessing. The Compensating Methods should be also closely connected to the Network Kernel, because they are mostly dependent on the network disturbances. Encoding of compensated frames is also carried out on the basis pf wavelet technology.

Decoding of key and compensated frames is realized using back-encoding using wavelet technology.

Postprocessing is aimed at video quality enhancement by means of applying filters to video image for sharpness and color spectrum improvement.

1. Key Frame Packaging is Illustrated in FIG. 9

The packaging process consists of seven stages as shown by FIG. 9.

Description of Stage 1.1 as in FIG. 10: static frame in the RGB format is inputted. The frame is constituted of three planes: red, green and blue that together make up an image. Using standard, one-one functions, static frame is converted to another format called YUV, that, in its turn, is also a unity of three planes: brightness constituent Y and two color sub carriers, modulated by color signals U and V. The most used formulas for YUV conversion: Y=0.299*R+0.587*G+0.114*B U=0.564*(B−Y) V=0.649*(R−Y)

Such presentation of an image is more informative for further analysis.

Description of Stage 1.2 as in FIG. 11: Static frame in YUV format is inputted. With the help of two filters based on wavelets the image is being resolved into 2 constituents: high frequency and low frequency. The conversion is one-one and at the output is presented as a graph at the junctions of which the coefficients, as the result of resolution are located. The arcs are the connections between the coefficients. In order to resolve a frame into a graph wavelet filters are used. The wavelet filters were selected experimentally and are the fittest for video packaging. (However, the wavelet filters can be easily modified, if necessary). The wavelet filters are hard coded in the program as at the transmitting side as well as at the receiving one (they should be similar at both sides).

Description of Stage 1.3 as in FIG. 12: In order to package the data at stages 4 and 5 the graph at stage 3 should meet the definite requirements.

Each graph junction, except for the most upper, should have a “parent.” At stage 3 we check a graph from stage 2 and complete it, if necessary, i.e. we indicate “parents” for the junctions that don't have any.

Description of Stage 1-4 as in FIG. 13: Beginning from this stage the packaging process starts. In order to make analysis at stage 5, graph from stage 3 should be subject to unique treatment and transformed into unique machine representation-bit planes.

Description of Stage 1.5 as in FIG. 14: The bit planes and contained there data from stage 4 are being analyzed. On basis of this analysis, we organize data within bit planes according to their significance. Then depending on the compression ratio value that Is used on this stage, we cast out all the data that is insignificant at this stage. (The greater compression ratio value, the more data is cast out). The data that remains is sorted out into 4 different data flows.

Description of Stage 1.6 as in FIG. 15: In order to achieve greater data compression, the data in the flows is organized in a special way and is subject to additional statistic analysis.

Description of Stage 1.7 as in FIG. 16: Organized flows are united into integrated structure, that is a packaged frame. The structure is then transferred for sending through network.

2. Building Up Frames (Compensating Method) (Shown in FIG. 17)

Stage I. Comparing to the Previous Frame and Establishing the Difference

Description: A static frame is inputted. The difference with the previous frame is established. There may be two variants: establishing the difference with the previous frame or establishing the difference with the previous basic frame. The first variant presupposes the smaller difference, but its absence in the communication moment will not allow building up the next frame. The second variant presupposes the greater difference, but absence of the frames will not be crucial.

Stage 2. Processing of the Difference

Description: The difference is being processed in order to cut out the unnecessary data and make it more compact (compression).

Stage 3. Packaging of the Difference

Description: For packaging the modification of key frame packaging method is used.

Audio Codec

Audio Codec encodes the audio flow synchronically with the video flow. The sound encoding implies the original realization of psycho-acoustic model of sound encoding. This realization has enabled to transmit the human speech using the 1400 BPS channel.

A Network Kernel (such as shown in FIG. 18 should secure the well-timed delivery of data and is responsible for monitoring of the network for the purpose of network disturbances detection and basing on the statistics accumulated carries out the adjustment of Video and Audio Compressors. Picture displays the structure of the one-way data transfer channel (requirements for this channel are listed below). This channel consists of three flows:

-   -   Video Channel     -   Audio Channel     -   Control Channel

Video Channel is responsible for video frames delivery from Video Compressor.

Audio Channel is responsible for audio flow delivery from Audio Compressor.

Control Channel is responsible for a wide range of service functions:

-   -   Carrying out of connection of two or more users of the clients         programs before the communication session starts.     -   Synchronizing of video and audio flows.     -   Network.     -   Notification on network disturbances and data loss.     -   Carrying out of short messages exchange between the users         (chat).

FIG. 19 illustrates requirements and functional specifications for the development of the program system for video conferencing over the internet.

All the system users must register at web site where they enter their name, e-mail and password for the system login. After a user has been registered, the system assigns to each user a unique number (U1D).

After the user has been registered in the system he/she can upload the PS to his/her own computer and install it.

A client can also pay with the credit card for additional services (options) in the system. The payments are carried out through CyberCash system and are registered on the Billing server.

Client Application

Client application has the following functions:

1. View and search for users in the database. This option is available in all versions of PS.

2. Request for authorization to add users to the Contact List. A user is added to the Contact List after authorization. This option is available in all versions of PS.

3. Sending of short messages to a user from the Contact List. This option is available in all versions of PS.

4. Chat with a user from the Contact List. This option is available in all versions of PS.

5. Viewing of audio and video flows from users that can translate video and audio flows and that have authorized the user to view video and audio flows. This option is available in all versions of PS.

6. Video conferencing point-to-point with another user of the system that is authorized to perform video conferencing. Video conferencing is available for users that paid for this option.

7. Video translation for multiple users. This option is available for users that paid for the authorization of video translating.

Requirements for client's hardware:

-   -   Intell PC with processor PII Celeron 600 MHz and     -   Memory 64 Mb and more     -   Sound card     -   Video camera     -   Either standard modem 56 BPS for dial-up connection or     -   Network card for connection to 10/100 MB network

Requirements for client's software:

-   -   OS Windows 98 OSR1, Windows Me, Windows 2000     -   Set of Direct Show drivers (cameras and sound cards must be         compatible with the drivers)     -   TCP/IP protocol driver         Server Applications

1. Connection Server.

-   -   Connection Server is an entry point for all users of the system.         It carries out the following functions:     -   Request for UID and password for registration in the system     -   Securing of permanent connection with the user during the         session     -   User's status test     -   Keeping the users list that are online at the current moment     -   Data communication between the client and higher services (for         their description see below)     -   Sending of short messages to the user and their storage In         Message DB in case of failure

2. Redirector

-   -   Redirector is a thin layer between the Connection Server and         higher services. It is responsible for balancing the load of         higher services.

3. Directory Servers

-   -   Directory Servers store the distributed database of users and         their Contact Lists. Redirector server is responsible for the         load of these servers.

4. Messages DB

-   -   Messages DB—is the server of unsent messages. All the messages         that due to any reasons could not be delivered to the addressee         by the Connection Server are sent to the Messages DB. When a         user logs in the system, the Connection Server checks the         availability of unsent messages for this user and if there are         any, it send them to the user.

5. Billing System

-   -   The system of user accounts storage. For each registered system         user there is a personal account. As default if is empty, i.e.         after a user has been registered in the system, he/she has         access to free system services only. If a user wants to make         payments for additional services, he/she can do it using the         credit card (via CyberCash system). When a user logs in the         system, the Connection Server requests for his/her status at the         Billing System and based on the user's status assigns the access         to additional services.

Requirements for server hardware in one embodiment:

-   -   Server with processor PIII 600 MHz and faster     -   Memory 128 Mb and more

Requirements for server software in one embodiment:

-   -   OS Windows 2000 Server     -   MSSQL Server 2000

FIG. 20 illustrates the functional specifications for the development of a program system for compression and transmission of video images.

The purpose of this project is development of program system (further referred as PS) for compression and transmission of video images using low bandwidth channels of wireless communication of all existing standards. The given PS is intended for carrying out of video conferences and video transmissions in real time mode using wireless communication and it will be used as prototype for hardware implementation. The technology being developed that is basic technology for PS must be also adaptable and scalable for wide channels (56 BPS and higher). This fact would allow to extend the PS to the video film broadcast system.

Structural Scheme of Program System

Client Part.

-   -   Client part is an independent program that was installed on         user's PC and that enables the user to transmit real time video         images to or to carry out real time video conference with         another user who has the same program installed on his PC. The         connection to another user is realized either using wireless         communication channel (direct connection) or using Internet (or         other TCP/IP networks). In case of connection using Internet (or         other TCP/IP networks) client part should be able to contact         with server program and to request about users who are connected         to the network at the moment.

Client part includes:

-   -   Video Compressor     -   Encodes video flow from video camera and transmits it to Network         Kernel     -   Decodes video flow from Network Kernel and transmits it to         user's display     -   Receives from Network Kernel network disturbances statistics and         corrects video flow parameters     -   Audio Compressor     -   Encodes audio flow from soundmap and transmits it to Network     -   Decodes audio flow from Network Kernel and transmits it to         soundmap     -   Receives from Network Kernel network disturbances statistics and         corrects audio flow parameters     -   Network Kernel     -   Realizes the connection between the two users     -   Realizes network data reception and transmission     -   Realizes control of transmitted data integrity     -   Realizes network monitoring and transmits network disturbances         statistics to Audio and Video Compressors

Description of data transmission principles are to be found in Network kernel description.

Requirements for client's hardware:

-   -   portable PC with processor PII Celeron 600 MHz and     -   memory 64 Mb and more sound card     -   sound card     -   video camera     -   connection device for connection to wireless communication         channel     -   either standard modem 56 BPS for dial-up connection or         Plan-Schedule of Works on the Project

Works on the project are realized in six stages.

1st stage Conciliatory and Preparatory. Presentation of the current version of the program.

-   -   During this stage the following work content should be         accomplished:     -   Developer prepares technical documentation and program modules         of the current version of program for video compression for         presentation;     -   Developer sets the task to personnel and makes sure that the         personnel adequately understands the project requirements;     -   Developer presents the current version of the program. During         the presentation the Developer should demonstrate:     -   1. Client part with possibility of direct connection by using         mobile phone and connection via Internet.     -   2. Realization of Video Compressor that operates observing the         hardware and software described in the given Requirements         Specifications.     -   3. Realization of Video and Audio Compressors that have         compensating mechanism and that transmits video and audio flows         in conferencing mode performing the acceptable quality with rate         of 3 frames per second using full duplex wireless communication         channel with bandwidth 9500 BPS and higher.     -   4. Realization of the current version of user interface.     -   5. Realization of chat functions.     -   6. Drawing up test record sheets of the current version of the         program that is capable to secure video flow transmission using         960O K5 channel.

2-nd stage<<Development of New Version>>.

-   -   Complete realization of server part.     -   Development, reconciliation and introduction of new version of         user.     -   Realization of Region of Interest methods.     -   Realization of two versions of Compensating models. Securing of         interaction between these methods and Network Kernel, that will         automatically change the settings of methods depending on the         network disturbances statistics.     -   Realization of Audio Compressor (the expected audio flow         bandwidth 1500 BPS)     -   Testing of the system with different OS, communication networks         standards and hardware.     -   Presentation of new version.     -   Drawing up test record sheets of the current version of the         program.     -   Transfer source codes to the Customer on the paper media.

3-d stage<<Preparatory work for realization of hardware version of codec>>.

-   -   User should have at his disposal a mechanism of adjustment to         different channel bandwidth, comprehensible functions for         quality adjustment of video and audio flows. All the specific         settings of Video and Audio Compressors should be realized         automatically without user's     -   User should also have at his disposal volume settings panel and         video camera parameters settings     -   User must be notified by program about the incoming call and be         able to shut off the undesired calls     -   User should have at his disposal the chat function         Server Part.

Server program is designed for the purpose of making easier the search and connection of client part users using Internet connection (or any other TCP/IP network). Server part is a scalable data base of the program users that can register and trace all the users connections to the client part of the network. Each program user when connected to the network can register on the server, add other users to his/her address book and to view the current status of any user listed in the address book. If the required user is online at the moment the server part should secure the possibility of fast connection to this user without making extra adjustments.

The main task of the billing system is to settle accounts with users for the time of using the channel. Payments for using the channel are collected for each minute. The cost of one minute is determined for each channel with possibility to introduce special tariffs for holidays, for example. Each client has a personal account. The money to this account is transferred from the client's credit card. Replenishment of the account is carried out by actual money transfer or by getting free minutes within the frames of advertising campaigns. Video broadcast servers send the requests to the billing server using http protocol. One billing server can serve several video broadcast servers.

-   -   Requirements for server hardware for one embodiment:     -   Server with processor PE 6D0 MHz and faster     -   Memory 128 Mb and more     -   Requirements for server software for one embodiment:     -   OS Windows 2000 Server     -   Requirements for the server part for one embodiment:     -   Server must have the standard scalable data base that supports         unlimited number of     -   Server must process not less than 10 D requests per second from         client programs

Network Kernel (such as FIGS. 18 or 21) should secure the well-timed delivery of data and is responsible for monitoring of the network for the purpose of network disturbances detection and basing on the statistics accumulated carries out the adjustment of Video and Audio Compressors. Picture #3 displays the structure of the one-way data transfer channel (requirements for this channel are listed below. This channel consists of three flows:

-   -   Video Channel     -   Audio Channel     -   Control Channel

Video Channel is responsible for video frames delivery from Video Compressor

Audio Channel is responsible for audio flow delivery from Audio Compressor

Control Channel is responsible for a wide range of service functions:

-   -   Carrying out of connection of too or more users of the clients         programs before the communication session starts     -   Synchronizing of video and audio flows     -   Network     -   Notification on network disturbances and data loss     -   Carrying out of short messages exchange between the users (chat)

Network Kernel requirements for one embodiment:

-   -   Control of data adequacy     -   Continuous network monitoring     -   Accumulating of network disturbances statistics and capability         of operation with Video and Audio Compressors settings     -   Availability of intelligent algorithms for working with         Compensating     -   Realization of chat functions     -   Scalability—the possibility to send one video flow to many         Interface

User Interface (GUI) must provide convenient and intuitively comprehensible form of managing the client program. GUI must secure an easy way of operation with program settings and simple and convenient connection to another user.

Requirements for User Interface (GUI) for one embodiment:

-   -   User Interface must be simple and intuitive     -   Interface must have a pleasant modern design     -   User Interface must consist of two dialogs for viewing the         incoming and outgoing video flows     -   User should have the possibility to enlarge the size of the         dialogs up to the size of the screen and to return the dialogs         to the reset state

Video Compressor should be capable for flexible adjustment during the video flow encoding process based on the statistics accumulated during the encoding process and on the statistics accumulated at and received from Network Kernel.

Requirements for Video Compressor for one embodiment:

-   -   Video Compressor should realize simultaneous encoding and         decoding of video flow in conferencing mode including         preprocessing and postprocessing following the software and         hardware requirements mentioned above     -   Video Compressor must provide symmetrical scheme of encoding and         decoding     -   The number of processed frames per second should be 5 and more         performing the acceptable quality using channel with bandwidth         of 9600 BPS     -   Compensating model should secure gradual quality Increase of         static image     -   Compensating model should be able to process possible network         disturbances     -   Compensating model must be realized in two variants: for         networks that guarantee data delivery (for further hardware         implementation using such networks) and for networks that do nor         guarantee data delivery (for networks of the Internet-type)         Audio Compressor

Audio Compressor carries out encoding and decoding using wavelets of audio flows. The realization of the given module must advance in two directions: use of available in the market standardized audio flow compression algorithms and analysis of possibilities to develop own audio codec based on the wavelet technology.

Requirements for Audio Compressor for one embodiment:

-   -   Audio Compressor should realize simultaneous encoding and         decoding of audio flow together with video in conferencing mode         following the software and hardware requirements mentioned above     -   Audio Compressor must provide symmetrical scheme of encoding and         decoding     -   Audio Compressor work must be synchronized with the video one         when     -   Sound quality must be sufficient for understanding the human         speech     -   Audio data volume must not exceed 240D BPS using channel with         bandwidth of 9600 BPS. The ideal volume is 1000 BPS     -   Audio Compressor should be able to process possible network         disturbances.     -   Network card for connection to 10/100 MB network

Requirements for client's software for one embodiment:

-   -   OS Windows 98 OSR 1, Windows Me, Windows 2000     -   Set of Direct Show drivers (cameras and sound cards must be         compatible with the drivers)     -   TCP/IP protocol driver over wireless communication channel

Requirements for data communication channels for one embodiment:

-   -   digital wireless communication channel     -   the given wireless communication channels should provide full         duplex communication with bandwidth 9600 BPS and higher     -   either direct dial-up connection between the two computer (or         connection via Internet using ASP) or     -   local 10/100 MB network for direct connection between the two         computers         Video Compressor

Video Compressor carries out encoding and decoding using wavelets of video flows. The given processor has the following work cycle:

-   -   Preprocessing     -   Encoding of key frames     -   Compensating models     -   Decoding of key and compensated frames     -   Postprocessing

Preprocessing—the necessary video image preparation for the following encoding, i.e. enhancement of quality (on the basis of available from the previous frames statistics).

Encoding of key frames is carried out on the basis of developed video compression methods using wavelet technology.

Compensating methods enable to transmit greater number of frames due to the fact that only the difference between them is being transmitted. This method should be closely connected with Preprocessing. The Compensating Methods should be also closely connected to the Network Kernel, because they are mostly dependent on the network disturbances. Encoding of compensated frames is also carried out on the basis of wavelet technology.

Decoding of key and compensated frames is realized using back-encoding using wavelet technology.

Postprocessing is aimed at video quality enhancement by means of applying filters to video image for sharpness and color spectrum improvement.

In the detailed description of the invention the concrete and the most preferable realization of the method is presented. The detailed description of the method steps and their specific parameters does not on any account mean that the invention is exhausted by the presented description. The additional advantages of the claimed method and its modifications as well can be found at its realization according to the general inventive ideas of the applicants. 

1. A method of data compression, said method comprising the steps: representing said data as an array D of wavelet decomposition coefficients, creating a tree map of said coefficients formed with a root node and consequently connected nodes wherein each node except the root node is a descendant of the corresponding ancestor, creating an array Z which components corresponding to said nodes are equal to 0 if the corresponding coefficient D has positive or zero value and they are equal to 1 if coefficient D has negative value, creating a set of threshold arrays T_(i)=T₀/2^(i), where T₀ is a basic threshold array, i is a threshold index, creating an array M whereas the value of M/T₀ ratio for each node is equal to maximum value of D/T₀ ratio among the all descendants of the given node, creating a set of arrays S_(i) which components are equal to 0 if the corresponding to given node value of array M component is less than the value of threshold array T_(i) component and equal to 1 if the corresponding value of array M component is equal or more than the value of threshold array T_(i) component, creating a set of arrays B_(i) which components are equal to the whole part of doubled fractional part of |D|/T₀ ratio. A method of claim 1 further comprising the steps of creating a V-set of vector-arrays V_(i) including the components of the arrays:
 2. S_(i), B_(i) corresponding to the descendants of the given node, and the components of the array Z_(i) corresponding to those descendants of the given node which B_(i) component is equal to 1: Creating data streams of V, S, B, Z components, for entropy coding procedures of said V, S, B, Z data streams.
 3. A method of claim 1 wherein the values of the components of basic threshold array T₀ are increased twice for each sequent subband. 